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- Flores, Olivier, et al.
(författare)
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An evolutionary perspective on leaf economics : phylogenetics of leaf mass per area in vascular plants
- 2014
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Ingår i: Ecology and Evolution. - : Wiley. - 2045-7758. ; 4:14, s. 2799-2811
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Tidskriftsartikel (refereegranskat)abstract
- In plant leaves, resource use follows a trade-off between rapid resource capture and conservative storage. This worldwide leaf economics spectrum consists of a suite of intercorrelated leaf traits, among which leaf mass per area, LMA, is one of the most fundamental as it indicates the cost of leaf construction and light-interception borne by plants. We conducted a broad-scale analysis of the evolutionary history of LMA across a large dataset of 5401 vascular plant species. The phylogenetic signal in LMA displayed low but significant conservatism, that is, leaf economics tended to be more similar among close relatives than expected by chance alone. Models of trait evolution indicated that LMA evolved under weak stabilizing selection. Moreover, results suggest that different optimal phenotypes evolved among large clades within which extremes tended to be selected against. Conservatism in LMA was strongly related to growth form, as were selection intensity and phenotypic evolutionary rates: woody plants showed higher conservatism in relation to stronger stabilizing selection and lower evolutionary rates compared to herbaceous taxa. The evolutionary history of LMA thus paints different evolutionary trajectories of vascular plant species across clades, revealing the coordination of leaf trait evolution with growth forms in response to varying selection regimes.
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- Sitnikov, Vasily, et al.
(författare)
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IceFormwork for Cast HPFRC Elements Process-Oriented Design of a Light-Weight High-Performance Fiber-Reinforced Concrete (HPFRC) Rain-Screen Facade
- 2019
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Ingår i: Ubiquity and Autonomy - Paper Proceedings of the 39th Annual Conference of the Association for Computer Aided Design in Architecture, ACADIA 2019. - : ACADIA. ; , s. 616-627, s. 616-627
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Konferensbidrag (refereegranskat)abstract
- The following paper introduces a design implementation of an innovative fabrication method that aims at enabling an environmental and automated production of geometrically challenging cast concrete elements. The fabrication method is based on the use of ice as the molding material for cast concrete. Empirical testing of ice CNC-processing, and a concrete mix capable of hardening at subzero temperatures was undertaken during previous research stages. The current paper illustrates a practical application of ice formwork. A facade rain screen has been developed using algorithmic modeling to illustrate a common case in which a non-repetitive geometrical pattern requires individual formwork to be produced for each element. Existing industrial methods capable of delivering such a project for formidable costs are based on CNC-processed expanded polystyrene (EPS), wood-based materials, or industrial wax formwork. These materials have been found to be either difficult to recycle, expensive, insufficiently strong, energy-or labor-intensive to produce. Preliminary evaluation has shown that ice, used in their place, facilitates a much cleaner, economic, and an even more energy-efficient process. Moreover, a very gentle demolding process through ice-thawing eliminates any shock stresses exposed on newly cast concrete and provides optimal curing conditions. As a result, the thickness of facade elements can be reduced while still fulfilling all structural requirements.
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